From apostrophe, due to use of apostrophes as single quotation marks to indicate boldface in ALGOL 60.[1] Other methods were used, especially in ALGOL 68, where the earlier matched apostrophes were no longer common,[2] and the term became used more generally for any such method.

^Proceedings of an International Conference on ALGOL 68 Implementation: Department of Computer Science, University of Manitoba, Winnipeg, June 18-20, 1974, ed. Peter R. King, University of Manitoba. Dept. of Computer Science, p. 148 – More serious problems are posed by "stropping," the technique used to distinguish boldface text from roman text. Some implementations demand apostrophes around boldface (whence the name stropping); others require backspacing and underlining; ...